The proposed research is aimed at gaining a comprehensive understanding of the relationship between structure and function in vascular and non-vascular smooth muscle during differentiation in vitro. To this end a multifaceted approach will be employed which includes a) studies of muscarinic and beta-adrenergic receptors by binding studies with radiolabelled ligands of high specificity and affinity for these receptors, namely 3H-quinuclidinyl benzylate and 125I-Hydroxybenzylipindolol; b) studies of surface topography, membrane architecture and membrane dynamics by a combination of fluorescence relaxation and electron microscopic techniques; c) studies of acetylcholinesterase and adenylate cyclase activities, and d) investigation of functional aspects of the system by quantitating the electrical and contractile response of cultured smooth muscle cells at various stages of development. For this aspect of the work, membrane potential sensitive fluorescent probes and a Coulter counter technique will be employed. Information derived from these various approaches will be correlated and integrated in order to obtain new insights into structure-function relationships in smooth muscle.